This invention relates generally to a filter element for filtering a liquid-state process stream.
Filter assemblies are used in many industrial facilities to selectively remove material from liquid-state process streams. Filter assemblies are used to both remove undesirable contaminates from process streams and to extract desirable filtrates out of process streams.
One type of filter assembly used in an industrial facility is a backwash filter assembly. This type of filter assembly typically includes a number of filter element sub-assemblies that are connected at opposed ends to common inlet and outlet manifolds. Liquid to be filtered is introduced to the filter element sub-assemblies through the inlet manifolds. The filtered liquid is ported from the filter element sub-assemblies through the outlet manifold. A flow diverter is positioned inside the inlet manifold of this assembly. The flow diverter is able to selectively connect the inlet end of each filter element sub-assembly to a drain line. A drive assembly, located outside of the inlet manifold, selectively moves the flow diverter between the individual filter element sub-assemblies.
When the filter assembly is in use, the liquid to be filtered flows through filter elements internal to the filter assembly. The material removed by the filter elements becomes trapped on the outer surfaces of the elements. Over time, a significant amount of trapped material builds up on the filter elements. The build up of this material eventually impedes the flow of liquid across the filter elements. In other words, the build up of this material causes a relatively large pressure drop to develop across the filter elements. In order to maintain the liquid flow through the filter elements at a reasonable rate, it is necessary to periodically remove the material that has adhered to the filter elements. This material removal is accomplished by backwashing the filter elements.
In backwashing, the flow diverter is set so as to establish a fluid communication path between the filter element to be backwashed and the drain line. A backwash liquid is flowed through the filter element in the direction opposite the direction through which the liquid that is filtered is flowed. Often, but not always, this backwash liquid is the filtered liquid that has just been discharged from the outlet ends of the remaining filter elements. The backwash liquid forces the material adhered to the side of the filter element off the filter element so the material flows down the drain. Often, a backwash filter system is operated so that the flow diverter periodically couples each filter element to the drain. By positioning the flow diverter in the inlet manifold, one filter element can be backwashed while the remaining filter elements continue to perform their filter function. Thus, a backwash filter system can both simultaneously filter the liquid that is flowed to it for filtering and backwash one of its filter elements.
Two backwash filter systems are disclosed in the Applicant""s Assignee""s U.S. Pat. Nos. 3,703,465 and 4,059,518.
While current backwash filter systems work reasonably well, there are some limitations associated with their use. The flow diverter of a typical backwash filter system is often subjected to the force of the stream of liquid that is introduced into the inlet manifold for filtering. The force of this liquid stream may cause the diverter to shift position. More particularly, the force of this fluid stream may cause unwanted rotational movement of the flow diverter when it is indexed from connection with one filter element to connection with a second fluid element. Thus, the drive assemblies of available flow diverters are typically provided with brake assemblies. These brake assemblies precisely regulate the rotational movement of the flow diverters to which they are attached. The need to provide this type of brake assembly typically adds to the cost of providing a backwash filter system.
Moreover, this type of brake assembly typically has at least two components that bear against each other. Over time, these components wear to the point at which they need to be replaced. Thus, the need to have to maintain the brake assembly incorporated into a backwash filter system contributes to the overall cost of maintaining the system.
Moreover, many backwash filter systems are designed so that the flow diverter internal to the system tightly seals against the opening of the filter element sub-assembly against which it is aligned. In order to maintain this seal, the flow diverter is typically pressed against an adjacent surface of the inlet manifold. This pressure typically results in the asymmetric loading of both the flow diverter and the seals located around the flow diverter. This asymmetric loading of these components, especially the seals, significantly accelerates the rate at which these components wear out and need to be replaced.
Still another disadvantage associated with backwash filter systems, as well as other kinds of filter systems, concerns the sub-assemblies used to hold the filter elements in their complementary housings. This sub-assembly must, naturally, provide a liquid tight barrier around the head end of the filter element with which it is associated in order to foster the operation of the element. Secondly, this sub-assembly must allow the filter element to be removable from the housing. Clearly, this is desirable so as to make it possible to replace, clean or repair the filter element as needed. However, these two objectives are, to a great extent, contradictory. Accordingly, the present sub-assemblies used to hold filter elements in their housings tend to be complex and/or expensive to provide.
This invention relates generally to a new and useful backwash filter system. The backwash filter system of this invention includes a flow diverter sub-assembly that is both economical to provide and relatively maintenance free to operate. The filter system of this invention also includes a coupling assembly for removably coupling a filter element into the complementary housing in which it is seated. The coupling assembly of this invention, in addition to providing the requisite liquid-tight barrier and allowing the filter element to be removed, is economical to provide.